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STKO seminar#

Displacement-based#

  • Requires a fine mesh for non-linear problems.
  • Characteristic length = element.
  • Shear not considered in sectionAggregator.
  • If torsion included in both fibersection and aggregator, set –GJ of fibersection = 0.
  • Element loads do not affect directly the section response.

Force-based#

  • One element per member is enough.
  • Characteristic length = gauss point.
  • Shear considered in sectionAggregator.
  • If torsion included in both fibersection and aggregator, set –GJ of fibersection = 0, or larger than torsional stiffness.
  • Element loads affect directly the section response.

Constraint Handler#

Wrong HANDLERS can lead to singularities.

Plain#

  • Condensate slave DOFs.
  • Pay attention to master-slave pairs.
  • Only for homogeneous constraints.
  • Only for identity constraint matrices.

Transformation#

  • Condensate slave DOFs.
  • Pay attention to master-slave pairs.

Lagrange#

  • Adds 1 row for each constraint equation.
  • The system is not positive-definite anymore.
  • Pay attantion to master-slave pairs.
  • Pay attention to duplicated constraints (over-constrained system).
  • Do not use convergence tests on displacements.

Penalty#

  • Does not change the system size.
  • Pay attention to the penalty parameters.
  • Do not use convergence tests on unbalance.